Cement grinding aid and pack set inhibitor



EXAMlNEB ice-9 3,094,425 Patented June 18, 1863 cement. Only a verysmall, economicall amount of this additive nee e used. It is believedthat 3,094,425 CEMENT GRlNlgflNfigiBlzfsrfgkAND PACK S the calciumacetate and -lignin sglfonaieiemain liquid or Alfred B. Adams, Melrose,Enmq-Earkas, Cambridge,

largely so dining the g rinding at elevated temperatures 5 and aremechanically dispersed over the nascent surfaces, ggg i j fiz zggg gg fia gl g' g ggyfi: at about the time of their formation. The additivesapbridge, Mass, a corporation of Connecticut Pear WW N0 Drawing Filed 21961, 57 place t e cement in the desired state of dry d1spers1on 7Claims, (31. 106-90) that results in improved grinding and millretention times 10 as well as facilitating subsequent storage andtransporting. This invention relates to a new composition of matter Itmay be that the sulfonate and acetate are taken up only useful forimproving the grindability of and reducing by the most active sites ofthe fresh surfaces, leaving the Mud cement and sirr il ar m a te ri alremainder of unneutralized portion of the surfaces to More par icuangtnnmcnncn proposes the use of a exert a beneficial effect duringgrinding and thereafter, combination of alignin sulphonate and calciumacetate or one may immediately seek the most active sites, while with,preferably, a catalyst or accelerator such as trithe other has a delayedaction effect. ethanolamine, as a cement additive. When this additiveThe data in the following table illustrate the effects that is added inamount of 0.01 to 0.05 weight percent (total the composition of thisinvention has on the grinding of solids) during the grinding of cementclinkers, it increases cement clinkers, on the ground cement and on themortar the grinding efficiency, and thereafter inhibits the occurmadetherefrom. The data appearing in this table were rence of pack set inthe field. obtained by testing individual batches of the same type IMost cements when compacted by vibration, e.g., when cement, each ofwhich was prepared in the following transported in a hopper car, becomesemi-rigid and will manner; the clinker was charged to a laboratorysteel ball not flow until considerable mechanical effort has beenapgrinding mill; the mill was closed and heated to a term plied to breakup the compaction, Thi condition is pcrature between 210 F. and 230 F.prior to rotation; known as pack et, and i to be distinguished from andthe additive was then placed in the mill by means of warehouse or bagset caused by incipient hydration. It a pipet Pushed through a hollowShaft- After fixed is known that a cement is less likely to pack set ifcertain fir 0f revolutions, taking about 70 minutes, the mill additivesare incorporated into the cement during or after was stopped and thepack set index and other properties grinding. of the ground cement weredetermined.

Cleavage of the particles during grinding of cement clinkers exposesfresh or nascent surfaces. The fresh TABLE surfaces have high energiesor reactivities probably be- Effect of Additives on Type I Cement causeof the breaking of ionic bonds. The surface forces ff ctihtepartiltglestperslis t for some time gfteir grirfidifiig and Iii/eight; Pk sComprlelssivei ea 0 pac se an /or poor cemen 111 ity l t ey are w "'180 trenet ,P-S- not properly reduced. Undue reduction or the completeAddltwe *fl figi i 23233 if; 531i, absence of surface forces orattraction between the cement Solids) 1 7 8 particles is undesirablebecause the cement becomes ex- 0 day days days cessively fluid orflowable. If, on the other hand, the surface forces are too great, thecement tends to pack set fi f; ;;;;;;;"-"55r i188 iii? 23 5; i233 and tohave low bulk densities because of the presence 04 3160 9 672 v 4,975 ofhigh void volume agglomerates. Low bulk densities f g' igijjjjj 88:3;}38 i8? 2 213% mean that less cement by weight can be stored in ahopper Or silo. 40 Notes;

What one wishes to achieve is an optimum or controlledB1ail1?Surfe.A1'eabY ASTM 0294- an by AS'IM Cl-a8I. state of drydispersion of the ground cement particles 1n Compressive strength byASTM 0109-58 (using2 inch cubes). air. Proper control of the dispersionof the particles in g'g Percent desuga'ed calcium lignin sulphmate (aswater the air-continuous phase leads to the desired degree of 50 oils-112A: as percent CLS with 14 percent triethanolamine (as 35-31, fluidityboth during and after grinding. 39 Water Solution):

. cid. percent acetic acid. it has been known that certain polarmolecules when Invention: 61.5 percent CLS, 10.5 percent TEA, and 25.0percent added to the cement either during or after grinding will calciumacetate 3537 Percent water attach to the particles and reduce theirsurface forces. If The composition of this invention identified in thetable the amount of additive used and/or if the time of addition 5? wasprepared in the following manner: 100 parts of water are not correct,however, optimum dry dispersion is not and 32 parts of triethanolaminewere added, with stirring, obtained. For example, if an unduly activeadditive is to 240 parts of des v d calcium lignin sulphonate. Thepresent during grinding, it will cause a cement to have an batch wasuniformW extreme fluidity while in the mill. This will result in the w 5added with stirring. cement passing rapidly through the mill before itis re- 60 Pack sefindex 1s a relative term which numerically indiducedto the desired size and thus in an increase in recates how prone aparticular cement is to pack set when cycle of oversized material. Thesame additive, however, it is stored or transported in bulk. The packset index is may give acceptable performance if mixed with the cementobtained in the following manner: 100 grams of cement after grinding.Conversely, an additive which produces are placed in a 250 cubiccentimeter Erlenmeyer flask the desired degree of dry dispersion whenground with set on top of the variable vibrator. The vibrator is a theclinker may or may not be effective if admixed after so SyntronSingle-Action paper jogger, Model PJ-4, havgrinding. While these generalprinciples are known, the ing a knob by means of which the vibration isadjusted. particular response that a cement will display to specific Thesame flask should be used for any series of tests. additives isdiflicult to predict. The flask should be placed in the same position ofthe In the present invention, it has been found that the 70 vibrator foreach test. A simple jig can be used to accomb-inatiop gf calcium acetatewith a lignin sulfonate fdtlie ceinnt mill and intergroiffidwitlrthecomplish this. ,The adjustable knob is set at F. and the Erlenmeyerflask containing the cement is vibrated for 15 seconds. After vibration,the flask is removed from the vibrator and fitted into a plywood jig,with the axis of the flask being horizontal. The flask is then rotatedaround its axis until the cement, which is compacted on the bottom ofthe flask, collapses. The Erlenmeyer flask is twisted with 180 turns atapproximately 100 twists per minute. The number of 180 twists requiredfor the cement sample to collapse establishes the pack set index.

The pack set index obtained by this method correlates well with thefield performance of the cement. The higher the pack set index of theparticular cement, the more prone a large volume of that cement is topack set if stored or transported in bulk.

The calcium lignin sulphonate and the calcium ligninsulphonate-triethanolamine mixture identified in the table arecommercially used additives. The surface area increases obtained withthe composition of this invention as compared to the blank and thecalcium lignin sulphonate compositions establishes that the presentcomposition improves grinding efliciencies to a somewhat greater extentthan the calcium lignin sulphonate composition, although a smalleramount of the sulphonate is used in the present composition.Experimental use of the present composition in two commercial plantshandling type I cement re sulted in average production increases of 8 to10 percent over the use of the sulphonate-amine additive.

As shown in the table, the improvement in the compressive strength ofthe cement was about the same as that obtained with the commerciallyused additives. The present additive had little effect on airentrainment.

The pack set indices show that the present composition materiallyameliorates the compacting tendency of cements. The improvement obtainedis about equal to that obtained with acetic acid at the 0.04 weightpercent level. It is better at the 0.02 weight percent level. Aceticacid is known to be one of the most effective pack set inhibitorsavailable (see U.S. Patent 2,857,286). Aside from its obnoxious odor andcorrosiveness, a pack set inhibiting amount of acetic acid is notusually added to a grinding mill because it excessively reducesretention time and impairs grinding rather than helping it. It isbelieved that while aciitic acid can be effectively added in smallamounts after grinding, its use during grinding gives adverse resultsbecause it vaporizes at the grinding temperature and becomes tooavailable to the nascent surfaces, resulting in excessive reduction ofthe surface forces and undue fluidity.

At one commercial plant the dispersing properties of this compositionpermitted a bulk car to be loaded with 4 lignin sulphonate after it hasbeen desugared, or it can beformed in situ during the desugaringoperation. Desugaring is usually accomplished by boiling the ligninsulphonate with lime water and thereafter neutralizing 5 the excesslime. The excess lime can be neutralized with the proper amount ofacetic acid, in place of the mineral acid normally used, to form thedesired amount of calcium acetate.

If the present composition is to be stored for some time, it isdesirable to add a small amount of bacteriocide,

such as phenol mercuric acetate.

The composition of this invention can most conveniently be prepared andhandled as a 25 to 40 weight percent (total solids) solution in water.

Having described this invention, what is sought to be protected byLetters Patent is succinctly set forth in the following claims.

What is claimed is:

1. As a Portland cement additive, 1 to parts of a 2 lignin sulphonateadmixed with 1 part by weight of calcium acetate.

W rinding aid and pack set inhibitor consisting essentiali WvHle?solution of 1 to 20 parts by weight of a lignin sulphonate, 1 part byweight of calcium acetate and 0 to 25 weight percent, based on thecombined weigth of the sulphonate and acetate of an amine accelerator.

' 3. The composition of claim 2 wherein said amine accelerator istriethanolamine.

4. A dry Portland cement containing about 0.01 to 0.05 weight m additiveconsisting essentially of 1 to 20 parts of calcium lignin sulphonate, 1part by weight of mlcium acetate and 0 to 25 weight percent of triethanolamine based on the combined weight of the sulfonate and acetate5. A proc'ewreducing the tendency of Portland cement to pack setcomprising admixing therewith l to 20 parts of a lignin sulphonate and 1part by weight of calcium acetate during the grinding of the cement.

6. The process of claim 5 wherein triethanolamine is also intergroundwith said cement in amount of about 0 to 25 weight percent based on thecombined weight of the sulfonate and acetate.

7. A grinding aid and pack set inhibitor for Portland cement consistingessentially of an aqueous solution of 2 to 5 parts by weight of calciumlignin sulphonate, 1

part by weight of calcium acetate, and 8 to 15 weight percent oftriethanolamine based on the combined weight of the sulphonate andacetate.

397.5 barrels of cement at the first filling, where normally only 375barrels of the cement could be charged when the sulphonate-aminecomposition was used during grinding.

The weight ratio of calcium lignin sulphonate to calcium acetate usedcan vary from 1/1 to 20/1. It is preferably in the range of 2/1 to 5/1.The amount of triethanolamine or equivalent catalyst or accelerator (seeU.S. Patent 2,031,621) is about 0 to 25 weight' percent of the combinedamounts of the sulphonate and acetate. The amount is preferably 8 to 15weight percent.

The calcium acetate can be added as such to the calcium References Citedin the file of this patent UNITED STATES PATENTS OTHER REFERENCES TLewis: A Review of By Products of Sulfite Pulping,

sfCl51)ASSn. of Pulp & Paper Ind., July 8, 1948 (pages

1. AS A PORTLAND CEMENT ADDITIVE, 1 TO 20 PARTS OF A LIGNIN SULPHONATEADMIXED WITH 1 PART BY WEIGHT OF CALCIUM ACETATE.